Pyridoxine 5′-phosphate oxidase is a candidate gene responsible for hypertension in Dahl-S rats

Recent advances in the identification of genes for human hypertension

It is a well-established fact that genes are involved in the etiology of hypertension. However, identification of the gene variants still remains a challenge. Over the years, different approaches and technologies, including genome-wide scans, case-control association studies, experiments on inbred rodent models and expression profiling, have been utilized to elucidate hypertension susceptibility genes, but so far the results have been equivocal. During the last year, further chromosomal regions harboring blood pressure loci have been identified, and transcriptomics has been applied to aid the identification of disease genes. There are great expectations for the future with regards to further advancements in transcriptomics and proteomics. This review reports primarily on work that has been carried out in the last 12 months in the field, and considers its contribution towards a better understanding of the genetic mechanisms involved in blood pressure regulation and hypertension.

Association of the catechol-O-methyl transferase gene Val158Met polymorphism with blood pressure and prevalence of hypertension: interaction with dietary energy intake

BACKGROUND

Previous studies of a functional variant of the catechol-O-methyl transferase (COMT) gene, Val158Met, have provided inconsistent results with regard to blood pressure or hypertension. We examined the effect of this variant, the considering environmental factors of daily salt and energy intakes.

METHODS

A total of 735 Japanese men (mean age, 47 years) were recruited from two separate occupational cohorts from Kanagawa and Kyoto prefectures. Participants were genotyped for the presence of COMT Val158Met (rs4680, G/A). Daily salt and energy intakes were evaluated by the food frequency questionnaire (FFQ).

RESULTS

Met/Met carriers had higher adjusted systolic blood pressure (SBP) (+4.79 mm Hg, P < 0.001) and diastolic blood pressure (DBP) (+2.33 mm Hg, P = 0.001) than Met/Val or Val/Val carriers. There was a significant association between being a Met/Met carrier and having a higher prevalence of hypertension (odds ratio = 2.448, 95% confidence interval = 1.426-4.205, P = 0.001). When salt and energy intakes were dichotomized, the effect of Val158Met on hypertension was observed only in the high-energy intake group, and was equivalent between low- and high-salt groups.

CONCLUSION

The Met allele of COMT Val158Met is associated with higher blood pressure and higher prevalence of hypertension in Japanese men, and energy intake may interact with this effect.

Genetic control of the corticosterone level at rest and under emotional stress in ISIAH rats with inherited stress-induced arterial hypertension

The genetic background of the regulatory systems of the hypothalamic-pituitary-adrenal (HPA) axis in hypertension remains unclear. The inherited stress-induced arterial hypertension (ISIAH) and Wistar Albino Glaxo (WAG) normotensive rats were bred and their F(2) progeny were used in a quantitative trait loci (QTL) analysis to identify genomic regions for plasma basal and stress-induced corticosterone levels, and for absolute and relative adrenal gland weights. The significant loci were found for stress-induced corticosterone on chromosome 9 and for adrenal weight on chromosome 6. The results may help to identify the genes controlling the trait phenotypes in the ISIAH rats characterized by the enhanced responsiveness to stressful stimulation.

Vitamin B6: a molecule for human health?

Vitamin B₆ is an intriguing molecule that is involved in a wide range of metabolic, physiological and developmental processes. Based on its water solubility and high reactivity when phosphorylated, it is a suitable co-factor for many biochemical processes. Furthermore the vitamin is a potent antioxidant, rivaling carotenoids or tocopherols in its ability to quench reactive oxygen species. It is therefore not surprising that the vitamin is essential and unquestionably important for the cellular metabolism and well-being of all living organisms. The review briefly summarizes the biosynthetic pathways of vitamin B₆ in pro- and eukaryotes and its diverse roles in enzymatic reactions. Finally, because in recent years the vitamin has often been considered beneficial for human health, the review will also sum up and critically reflect on current knowledge how human health can profit from vitamin B₆.

Identification of non-Alzheimer's disease tauopathies-related proteins by proteomic analysis

OBJECTIVES

To identify differentially expressed proteins between tauopathies cases and controls and to explore molecular mechanisms of tauopathies.

METHOD

Two-dimensional gel electrophoresis (2DE) was applied to separate the total proteins of temporal lobe obtained at autopsy from four tauopathies cases and four aged subjects without clinical or pathologic involvement of nervous system. The silver or Coomassie brilliant blue stained gels were analysed by 2-DE software Image Master 2D Elite. Selected differential protein spots were identified with MALDI-TOF/TOF tandem mass spectrometry.

RESULTS

Glyceraldehyde 3-phosphate dehydrogenase, uracil DNA glycosylase, human superoxide dismutase, isocitrate dehydrogenase subunit, synaptotagmin I, thioredoxin peroxidase 1, glial fibrillary acidic protein, P25 alpha, enoyl coenzyme A hydratase short chain 1, pyridoxine-5'-phosphate oxidase, Mn-superoxide dismutase and alpha enolase were significantly upregulated in tauopathies brains, whereas antioxidant protein 2, ferritin heavy chain, glutamate dehydrogenase precursor, peptidyl-prolyl cis-trans isomerase A, serum albumin precursor and dihydropyrimidinase-related protein 2 were lowly expressed in tauopathies brains.

CONCLUSIONS

We identified a number of tauopathy-related proteins that might be useful for discovering the molecular mechanisms of tauopathies, which could also be helpful for diagnosing and treating these disorders.

Catechol O-methyltransferase val158-met polymorphism is associated with abdominal obesity and blood pressure in men

Catechol O-methyltransferase (COMT) degrades catecholamines and estrogens, both of which are of known importance for cardiovascular risk factors such as obesity and hypertension. The gene coding for COMT contains a val158-met polymorphism that exerts a considerable influence on enzymatic activity. We hypothesized that this polymorphism might influence risk factors for cardiovascular disease. Deoxyribonucleic acid samples and data regarding blood pressure and anthropometry were collected from 240 Swedish men, all 51 years old. Subjects homozygous for the low-activity allele (met) displayed higher blood pressure, heart rate, waist-to-hip ratio, and abdominal sagittal diameter as compared with heterozygous subjects, who in turn displayed higher blood pressure, heart rate, waist-to-hip ratio, and abdominal sagittal diameter than subjects homozygous for the high-activity allele (val). All measured variables were significantly correlated; however, the associations between COMT val158-met and cardiovascular variables, and the association between COMT val158-met and anthropometry, respectively, were partly independent of each other, as revealed by multiple linear regression.

Exclusion of the Catechol-O-Methyltransferase Gene from Genes Contributing to Salt-Sensitive Hypertension in Dahl Salt-Sensitive Rats

Catechol-O-methyltransferase (COMT) is an enzyme that inactivates catecholamines. Several studies have suggested that this enzyme may play a role in blood pressure regulation. We previously reported that the expression levels of Comt mRNA in Dahl salt-sensitive (DS) rats were lower than those in Lewis (LEW) rats. However, the physiological significance of this phenomenon has not been investigated. The purpose of the present study was to evaluate the significance of lower expression of Comt in Dahl salt-sensitive hypertension. The Comt gene in DS rats has a palindromic insertion in 3'-untranslated region, which appears to be responsible for reduced mRNA stability. A genome-wide quantitative trait loci (QTL) analysis of blood pressure using 107 F2 rats indicated that a statistically significant QTL for pulse pressure was located at the Comt locus in chromosome 11. Microarray analysis confirmed that Comt was the only gene differentially expressed between DS and LEW rats in this chromosomal region. However, COMT inhibitors had no significant effects on blood pressure in either DS or LEW rats. Thus, Comt was excluded from the candidate genes contributing to salt-sensitive hypertension in DS rats. A true gene responsible for pulse pressure in this chromosome 11 region remains to be determined.

Association of genetic polymorphisms of ACADSB and COMT with human hypertension

OBJECTIVES

Genetically hypertensive rats provide an excellent model to investigate the genetic mechanisms of hypertension. We previously identified three differentially expressed genes, Acadsb (short/branched chain acyl-CoA dehydrogenase), Comt (catecholamine-O-methyltransferase), and Pnpo (pyridoxine 5'-phosphate oxidase), in hypertensive and normotensive rat kidneys as potential susceptibility genes for rat hypertension. We examined the association of human homologues of these genes with human hypertension.

METHODS

We sequenced three genes using samples from 48 or 96 hypertensive patients, identified single nucleotide polymorphisms, and genotyped them in a population-based sample of 1818 Japanese individuals (771 hypertensive individuals and 1047 controls).

RESULTS

After adjustments for age, body mass index, present illness (hyperlipidaemia, diabetes mellitus), and lifestyle (smoking, alcohol consumption), multivariate logistic regression analysis revealed that -512A>G in ACADSB was associated with hypertension in women (AA vs AG + GG: odds ratio = 0.70, 95% confidence interval = 0.53-0.94). This single nucleotide polymorphism was in tight linkage disequilibrium with -254G>A. Furthermore, -1187G>C in COMT was associated with hypertension in men (GG vs CG + CC: odds ratio = 0.69, 95% confidence interval = 0.52-0.93) and was in tight linkage disequilibrium with 186C>T. After adjustments described above, -512 A>G and -254G>A in ACADSB were associated with variations in systolic blood pressure. ACADSB was in tight linkage disequilibrium with MGC35392 across a distance of 18.3 kb. COMT was not in linkage disequilibrium with any adjacent genes. Analysis indicated that two haplotypes of COMT were significantly associated with hypertension in men.

CONCLUSION

Our study suggests the possible involvement of genetic polymorphisms in ACADSB and COMT in essential hypertension in the Japanese population.

Transcriptome analysis and kidney research: Toward systems biology

An enormous amount of data has been generated in kidney research using transcriptome analysis techniques. In this review article, we first describe briefly the principles and major characteristics of several of these techniques. We then summarize the progress in kidney research that has been made by using transcriptome analysis, emphasizing the experience gained and the lessons learned. Several technical issues regarding DNA microarray are highlighted because of the rapidly increased use of this technology. It appears clear from this brief survey that transcriptome analysis is an effective and important tool for question-driven exploratory science. To further enhance the power of this and other high throughput, as well as conventional approaches, in future studies of the kidney, we propose a multidimensional systems biology paradigm that integrates investigation at multiple levels of biologic regulation toward the goal of achieving a global understanding of physiology and pathophysiology.

Klk1 as One of the Genes Contributing to Hypertension in Dahl Salt-Sensitive Rat

A genome-wide quantitative trait loci analysis for blood pressure was performed using 107 male F 2 rats derived from Dahl salt-sensitive and Lewis rats. Blood pressure was assessed by telemetry, and >400 microsatellite markers were used for genotyping. Two major quantitative trait loci for blood pressure were identified at chromosome 1 and chromosome 10. The expression levels of 366 transcripts around the chromosome 1 quantitative trait loci were assessed by RT-PCR, and we found that the Klk1 (kallikrein 1) and Ngfg (nerve growth factor gamma) mRNA levels were significantly reduced in the kidneys of Dahl salt-sensitive rats compared with those in Lewis rats. The expression levels of kallikrein 1 protein were also suppressed in Dahl salt-sensitive rats compared with those in Lewis rats. Because the kallikrein–kinin system has been shown to be involved in renal function, including salt homeostasis, it is likely that the reduced expression of Klk1 contributes to salt-sensitive hypertension in Dahl salt-sensitive rats.